Comparing Price Indices of Clothing and Footwear for Scanner Data and Web Scraped Data

[eng] Statistical institutes are considering web scraping of online prices of consumer goods as a feasible alternative to scanner data. The lack of transaction data generates the question whether web scraped data are suited for price index calculation. This article investigates this question by comparing price indices based on web scraped and scanner data for clothing and footwear in the same webshop. Scanner data and web scraped prices are often equal, with the latter being slightly higher on average. Numbers of web scraped product prices and products sold show remarkably high correlations. Given the high churn rates of clothing products, a multilateral method (Geary-Khamis) was used to calculate price indices. For 16 product categories, the indices show small overall differences between the two data sources, with year on year indices differing only by 0.3 percentage point at COICOP level (men’s and women's clothing). It remains to be investigated whether such promising results for web scraped data will also be found for other retailers.